1. Field of the Invention
The present invention relates to an electrical snap-action switch. It is formed by an arched elastic sheetmetal member which, when subjected to compressive stress by an actuating element, is capable of rapidly snapping from a stable position into a metastable position, thus effecting the closing and/or opening of contacts.
2. Description of the Prior Art
Electrical snap-action switches operating on the arched elastic sheetmetal member principle, providing snap actions in response to changes in pressure exerted upon the arch are known.
As an example, the German Pat. No. 458,899 discloses an electrical snap-action switch using a snapping spring element consisting of at least two flat springs which are joined at the ends. In this case the spring element is designed in such a way that the one flat spring is shorter than the other one. Because of the difference in lengths, when the flat springs are joined to one another at their ends, at least one is arched and they can be caused to snap-over by actuating them at the ends where they are joined to one another. Such snapping elements consisting of several different long flat springs joined to one another, however, are not easy to manufacture, and a snap-action switch employing such spring elements has a rather complicated construction.
Moreover, from the German Published Patent Application (DOS) No. 21 02 218 there is known an electrical switch comprising a snapping spring element, in which the spring element has a frame-like construction and projections are arranged in the recess of the frame, to be bent out of the plane of the spring by means of a suitable actuating element. By bending out this projection there is achieved a snapping of the frame parts towards the one or the other side, which is utilized for actuating switching contacts. Also in this case the spring element has a complicated construction and requires expensive actuating devices.
Furthermore, these conventional types of snap-action switches still have the disadvantage of having to be reactuated subsequently to the snapping over, to enable them to return to their original switch position.
Finally, from the German Published Patent Application (DOS) No. 23 06 268 there is known a switch employing a snapping spring element having the shape of a round arched plate spring. In this type of switch the spring element, subsequent to being snapped-over, assumes a metastable position so as to snap back into the original position as soon as the pressure ceases to be exerted by the actuating element. The plate shaped spring element, in this case, rests on an angular (ring shaped) contact which must be so high as to permit the spring to be pushed through beyond its plane position. The contacts to be actuated are arranged on circular lines concentrically in relation to the supporting ring of the spring. In this conventional type of switch, of course, the spring element is of a very simple design, but the contact travel paths are very short, so that only very low voltages can be switched apart from any danger resulting from a short-circuit in the event of soiling, or contamination, of the contacts.